High frequency of immature dendritic cells and altered in situ production of interleukin-4 and tumor necrosis factor-α in lung cancer

INTRODUCTION: Antigen-presenting cells, like dendritic cells (DCs) and macrophages, play a significant role in the induction of an immune response and an imbalance in the proportion of macrophages, immature and mature DCs within the tumor could affect significantly the immune response to cancer. DCs and macrophages can differentiate from monocytes, depending on the milieu, where cytokines, like interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) induce DC differentiation and tumor necrosis factor (TNF)-alpha induce DC maturation. Thus, the aim of this work was to analyze by immunohistochemistry the presence of DCs (S100+ or CD1a+), macrophages (CD68+), IL-4 and TNF-alpha within the microenvironment of primary lung carcinomas. RESULTS: Higher frequencies of both immature DCs and macrophages were detected in the tumor-affected lung, when compared to the non-affected lung. Also, TNF-alpha-positive cells were more frequent, while IL-4-positive cells were less frequent in neoplastic tissues. This decreased frequency of mature DCs within the tumor was further confirmed by the lower frequency of CD14-CD80+ cells in cell suspensions obtained from the same lung tissues analyzed by flow cytometry. CONCLUSION: These data are discussed and interpreted as the result of an environment that does not oppose monocyte differentiation into DCs, but that could impair DC maturation, thus affecting the induction of effective immune responses against the tumor.     

Induction of CD83+CD14+ nondendritic antigen-presenting cells by exposure of monocytes to IFN-alpha

IFN-alpha is a well-known agent for treatment of viral and malignant diseases. It has several modes of actions, including direct influence on the immune system. We investigated IFN-alpha effects on PBMC in terms of dendritic cell (DC) differentiation, as PBMC are exposed to high IFN-alpha levels during treatment of infections and cancers. We show that in vitro IFN-alpha exposure induced rapid and strong up-regulation of the DC-maturation markers CD80, CD86, and CD83 in bulk PBMC. Consistently, IFN-alpha induced up-regulation of these molecules on purified monocytes within 24 h. Up-regulation of CD80 and CD83 expression was IFN-alpha concentration-dependent. In contrast to GM-CSF + IL-4-generated DCs, most of the IFN-alpha-challenged CD83(+) cells coexpressed the monocyte marker CD14. Despite a typical mature DC immunophenotype, IFN-alpha-treated monocytes conserved phagocytic activity and never acquired a dendritic morphology. In mixed lymphocyte reactions IFN-alpha-treated monocytes were less potent than GM-CSF + IL-4-generated DCs but significantly more potent than untreated monocytes to induce T cell proliferation in bulk PBMC. However, only GM-CSF + IL-4-generated DCs were able to induce a significant proliferation of naive CD4(+) T cells. Notably, autologous memory CD4(+) T cells proliferated when exposed to tetanus toxoid-pulsed IFN-alpha-treated monocytes. At variance with untreated or GM-CSF + IL-4-exposed monocytes, those challenged with IFN-alpha showed long-lasting STAT-1 phosphorylation. Remarkably, CD83(+)CD14(+) cells were present in varicella skin lesions in close contact with IFN-alpha-producing cells. The present findings suggest that IFN-alpha alone promptly generates nondendritic APCs able to stimulate memory immune responses. This may represent an additional mode of action of IFN-alpha in vivo.     

Requirement of mature dendritic cells for efficient activation of influenza A-specific memory CD8+ T cells

It is critical to identify the developmental stage of dendritic cells (DCs) that is most efficient at inducing CD8+ T cell responses. Immature DCs can be generated from monocytes with GM-CSF and IL-4, while maturation is accomplished by the addition of stimuli such as monocyte-conditioned medium, CD40 ligand, and LPS. We evaluated the ability of human monocytes and immature and mature DCs to induce CD8+ effector responses to influenza virus Ags from resting memory cells. We studied replicating virus, nonreplicating virus, and the HLA-A*0201-restricted influenza matrix protein peptide. Sensitive and quantitative assays were used to measure influenza A-specific immune responses, including MHC class I tetramer binding assays, enzyme-linked immunospot assays for IFN-gamma production, and generation of cytotoxic T cells. Mature DCs were demonstrated to be superior to immature DC in eliciting IFN-gamma production from CD8+ effector cells. Furthermore, only mature DCs, not immature DCs, could expand and differentiate CTL precursors into cytotoxic effector cells over 7 days. An exception to this was immature DCs infected with live influenza virus, because of the virus's known maturation effect. Finally, mature DCs pulsed with matrix peptide induced CTLs from highly purified CD8+ T cells without requiring CD4+ T cell help. These differences between DC stages were independent of Ag concentrations or the number of immature DCs. In contrast to DCs, monocytes were markedly inferior or completely ineffective stimulators of T cell immunity. Our data with several qualitatively different assays of the memory CD8+ T cell response suggest that mature cells should be considered as immunotherapeutic adjuvants for Ag delivery.     

Mature dendritic cells derived from human monocytes within 48 hours: a novel strategy for dendritic cell differentiation from blood precursors

It is widely believed that generation of mature dendritic cells (DCs) with full T cell stimulatory capacity from human monocytes in vitro requires 5-7 days of differentiation with GM-CSF and IL-4, followed by 2-3 days of activation. Here, we report a new strategy for differentiation and maturation of monocyte-derived DCs within only 48 h of in vitro culture. Monocytes acquire immature DC characteristics by day 2 of culture with GM-CSF and IL-4; they down-regulate CD14, increase dextran uptake, and respond to the inflammatory chemokine macrophage inflammatory protein-1alpha. To accelerate DC development and maturation, monocytes were incubated for 24 h with GM-CSF and IL-4, followed by activation with proinflammatory mediators for another 24 h (FastDC). FastDC expressed mature DC surface markers as well as chemokine receptor 7 and secreted IL-12 (p70) upon CD40 ligation in the presence of IFN-gamma. The increase in intracellular calcium in response to 6Ckine showed that chemokine receptor 7 expression was functional. When FastDC were compared with mature monocyte-derived DCs generated by a standard 7-day protocol, they were equally potent in inducing Ag-specific T cell proliferation and IFN-gamma production as well as in priming autologous naive T cells using tetanus toxoid as a model Ag. These findings indicate that FastDC are as effective as monocyte-derived DCs in stimulating primary, Ag-specific, Th 1-type immune responses. Generation of FastDC not only reduces labor, cost, and time required for in vitro DC development, but may also represent a model more closely resembling DC differentiation from monocytes in vivo.     

Induction of dendritic cell maturation by IL-18

IL-18 is a pluripotent proinflammatory cytokine produced primarily by antigen presenting cells involved in numerous aspects of immune regulation most notably on lymphoid cells. The effect of IL-18 stimulation on cells in the myeloid compartment, however, has been poorly studied. Human monocytes did not respond to IL-18. However, the human myelomonocytic cell line KG-1 and monocyte-derived dendritic cells (generated by GM-CSF+IL-4) showed a marked increase in CD83, HLA-DR, and several costimulatory molecules upon stimulation with IL-18. Furthermore, IL-18 decreased pinocytosis of these cells and increased their ability to stimulate alloreactive T cell proliferation, all characteristics of mature dendritic cells. These results suggest that IL-18 is involved in the maturation of myeloid DCs, but not differentiation of monocytes into DCs. The finding that IL-18 is involved in the maturation of dendritic cells is both novel and unexpected and indicates another important role for IL-18 as a key regulator of immune responses.     

Cytokines in the generation and maturation of dendritic cells: recent advances

Dendritic cells (DCs) are extremely efficient antigen presenting cells (APCs) that are potent stimulators of both T and B cell-mediated immune responses. Although DCs are normally present in very small numbers in the peripheral blood (PB), recent advances have made it possible to generate relatively large numbers of cells in culture. DCs can be differentiated in vitro from various cellular sources, including bone marrow (BM), cord blood (CB) and PB mononuclear cells (PBMCs). Although a wide variety of conditions have been reported to be able to support DC generation, the majority of research and clinical protocols to date differentiate DCs from precursors using granulocyte-macrophage colony stimulating factor (GM-CSF) in combination with either tumor necrosis factor-(TNF-)alpha or interleukin (IL)-4. However, a diverse array of cytokines has been shown to be able to induce DC differentiation under a variety of conditions. According to recent reports, cytokines such as IL-2, IL-6, IL-7, IL-13, IL-15 and hepatocyte growth factor (HGF), in combination or even, in some cases, alone, can contribute to the generation of DCs from either monocytes or CD34+ cells. Although the majority of cytokine combinations include GM-CSF, some do not. For example, Flt3 ligand (FL), in conjuction with IL-6 (in the absence of GM-CSF), has been reported to be able to induce DC differentiation from BM cells in a murine system. Other agents can play a dual role in DC activity. CD40 ligand (CD40L), as a single agent, has been shown to be able to generate DCs from PB monocytes, while numerous other reports have also demonstrated its role as a potent maturation factor. In contrast, for other cytokines such as IL-16 or IL-17, although there is no data for a role in DC generation, they have been reported to be involved in promoting DC maturation in vitro as defined by upregulation of costimulatory molecules, major histocompatibility complex (MHC) antigens and antigen presenting/T lymphocyte stimulatory capacity. Furthermore, cytokines such as stem cell factor (SCF) and FL have been shown to dramatically enhance in vivo DC recovery. The wide variety of cytokines and conditions that have been shown to be able to influence DC differentiation and activity to amply demonstrate the extreme heterogeneity found in the DC population, something that is reflected in the diverse phenotypes, functions and ontogeny displayed by DCs. This diversity may account for the large number of roles that have been attributed to DCs in the development and function of the immune system and, in turn, emphasizes the potential as well as the challenges of modifying specific aspects of the immune response system by manipulating specific DC subpopulations.     

Butyrate inhibits functional differentiation of human monocyte-derived dendritic cells

Dendritic cells (DCs) play a key role in immune function through antigen presentation by MHC and CD1, as well as cytokine production that shapes the immune response. Here we report that butyrate, a histone deacetylase inhibitor, inhibits the functional differentiation of human monocyte-derived DCs. Mature DCs were generated from monocytes in the presence of granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), followed by 2 day LPS stimulation. Butyrate treatment throughout the culture period inhibited the expression of CD1 molecules, but not on CD83, CD86, and MHC molecules. The suppression was exerted at protein and mRNA levels. Butyrate-treated immature DCs also showed decreased expression of CD1 molecules. Moreover the butyrate-treated immature DCs showed lower production of IL-12 p40 and IL-6 in response to lipopolysaccharides and induced less Th1 cells in allogenic mixed lymphocyte reactions. Our results imply that histone acetylation is involved in regulating immune responses through regulating functional differentiation of DC. Thus HDAC may be one of the targets for controlling the immune response.     

TNF skews monocyte differentiation from macrophages to dendritic cells

Monocytes represent a large pool of circulating precursors of APCs, both macrophages and dendritic cells (DCs). It is thus important to identify the mechanisms by which microenvironment regulates monocyte differentiation. We have previously shown that, upon contact with resting stromal cells such as fibroblasts, monocytes differentiate into macrophages in an IL-6/M-CSF-dependent fashion. Yet, in the inflamed tissue, monocytes need to yield DCs for the adaptive immunity to be induced. Inasmuch as TNF and IL-1 are present at the site of inflammation, we tested their capacity to modulate monocyte differentiation into either macrophages or DCs. TNF, but not IL-1, induce monocytes to become DCs despite the presence of fibroblasts. TNF-induced DCs contain Langerin-positive cells and are able to induce allogenic T cell proliferation. Then, TNF was found to decrease the expression and internalization of the M-CSF receptor, thus overriding the IL-6/M-CSF pathway. Thus, TNF facilitates the induction of adaptive immunity by promoting DC differentiation not only from CD34+ progenitors but also from CD14+ blood precursors.     

Production of functional dendritic cells from menstrual blood��a new dendritic cell source for immune therapy

Dendritic cells (DCs) are the most professional antigen-presenting cells of the mammalian immune system. They are able to phagocytize, process antigen materials, and then present them to the surface of other cells including T lymphocytes in the immune system. These capabilities make DC therapy become a novel and promising immune-therapeutic approach for cancer treatment as well as for cancer vaccination. Many trials of DC therapy to treat cancers have been performed and have shown their application value. They involve harvesting monocytes or hematopoietic stem cells from a patient and processing them in the laboratory to produce DCs and then reintroduced into a patient in order to activate the immune system. DCs were successfully produced from peripheral, umbilical cord blood-derived monocytes or hematopoietic stem cells. In this research, we produced DCs from human menstrual blood-derived monocytes. Briefly, monocytes were isolated by FACS based on FSC vs. SSC plot from lysed menstrual blood. Obtained monocytes were induced into DCs by a two-step protocol. In the first step, monocytes were incubated in RPMI medium supplemented with 2% FBS, GM-CSF, and IL-4, followed by incubation in RPMI medium supplemented with α-TNF in the second step. Our data showed that induced monocytes had typical morphology of DCs, expressed HLA-DR, HLA-ABC, CD80 and CD86 markers, exhibited uptake of dextran-FITC, stimulated allogenic T cell proliferation, and released IL-12. These results demonstrated that menstrual blood can not only be a source of stromal stem cell but also DCs, which are a potential candidate for immune therapy.     

Bryostatin-1 in combination with calcium ionophore promotes the maturation of human umbilical cord-blood monocyte-derived dendritic cells capable of activating neonatal alloreactive T cells

We have investigated the effect of bryostatin-1 (Bryo-1) and calcium ionophore (CI) on maturation and functions of DCs generated from adherent cells of cord blood cultured with GM-CSF plus IL-4 (CB-DCs). The CB-DCs treated with Bryo-1+CI exhibited morphologic characteristics of mature DCs, expressed increased levels of CD1a, CD80, CD83, CD86, and MHC class II as well as enhanced ability to induce proliferation of alloreactive T cells isolated from cord blood and IFN-gamma production. Treatment of CB-DCs with TNF-alpha or PMA+CI was less effective. Thus, Bryo-1+CI promotes maturation of CB-DCs and therefore could be used to enhance the neonatal immune response.     

Phagocytosis, a potential mechanism for myeloid-derived suppressor cell regulation of CD8+ T cell function mediated through programmed cell death-1 and programmed cell death-1 ligand interaction

CD8(+) T cells become exhausted, inducing cell surface protein programmed cell death-1 (PD-1) as chronic virus diseases or tumors progress, but underlying mechanisms of this are unclear. We previously showed that M-CSF is important for developing tolerogenic dendritic cells (DCs) from human CD14(+) monocytes. In this article, we identify M-CSF-derived DCs (M-DCs) after stimulation with IL-10 as myeloid-derived suppressor cells with additional tolerogenic activities to CD8(+) T cells. IL-10 increased PD-1 ligand expression on M-DC, and IL-10-stimulated M-DCs (M-DC/IL-10) induced expression of PD-1 on, and apoptosis of, CD8(+) T cells and phagocytosed CD8(+) T cells. Enhanced phagocytic activity of M-DC/IL-10 required IFN-γ, which further increased PD-1 ligand and PD-2 ligand expression on M-DC/IL-10. IFN-γ-stimulated M-DC/IL-10 cells were phenotypically macrophage-like cells with little or no expression of CD86, a costimulatory molecule, but with high expression levels of CD14, CD200R, and CD80. No phagocytic activity was detected with GM-CSF-derived DCs. We propose that phagocytosis by IFN-γ-stimulated M-DC/IL-10 cells, which may be DCs or, alternatively, a unique subset of macrophages, may be a mechanism by which IFN-γ-producing CD8(+) T cells are tolerized after type 1 immune responses to chronic virus or tumor, and that IFN-γ links effector CD8(+) T cells to their phagocytic clearance.     

Novel IL-15 dendritic cells have a potent immunomodulatory effect in immunotherapy of multiple myeloma

Dendritic cells (DCs) are the most potent antigen-presenting cells, and have thus been used in clinical cancer vaccines. However, the effects of DC vaccines are still limited, leading researchers to explore novel ways to make them effective. In this study, we investigated whether human monocyte-derived DCs generated via the addition of interleukin 15 (IL-15) had a higher capacity to induce antigen-specific T cells compared to conventional DCs. We isolated CD14⁺ monocytes from peripheral blood from multiple myeloma (MM) patients, and induced immature DCs with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 in the presence or absence of IL-15 for 4–6 days. Then we generated mature DCs (mDCs) with lipopolysaccharide for another 2 days [IL-15 mDCs (6 days), IL-15 mDCs (8 days), and conventional mDCs (8 days)]. IL-15 mDCs (6 days) showed higher expression of MHC I and II, CD40, CD86, and CCR7, and the secretion of IFN-γ was significantly higher compared to conventional mDCs. IL-15 mDCs (6 days) showed superior polarization of naïve T cells toward Th1 cells and a higher proportion of activated T cells, cytokine-induced killer (CIK) cells, and natural killer (NK) cells for inducing strong cytotoxicity against myeloma cells, and lower proportion of regulatory T cells compared to conventional mDCs. These data imply that novel multipotent mDCs generated by the addition of IL-15, which can be cultivated in 6 days, resulted in outstanding activation of T cells, CIK cells and NK cells, and may facilitate cellular immunotherapy for cancer patients.     

IFN-alpha skews monocyte differentiation into Toll-like receptor 7-expressing dendritic cells with potent functional activities

IFN-alpha is an important cytokine for the generation of a protective T cell-mediated immune response to viruses. In this study, we asked whether IFN-alpha can regulate the functional properties of dendritic cells (DCs). We show that monocytes cultured in the presence of GM-CSF and IFN-alpha can differentiate into DCs (IFN-alpha-derived DCs (IFN-DCs)). When compared with DCs generated in the presence of GM-CSF and IL-4 (IL-4-derived DCs), IFN-DCs exhibited a typical DC morphology and expressed, in addition to DC markers CD1a and blood DC Ag 4, a similar level of costimulatory and class II MHC molecules, but a significantly higher level of MHC class I molecules. After maturation with CD40 ligand, IFN-DCs up-regulated costimulatory, class I and II MHC molecules and expressed mature DC markers such as CD83 and DC-lysosome-associated membrane protein. IFN-DCs were endowed with potent functional activities. IFN-DCs secreted large amounts of the inflammatory cytokines IL-6, IL-10, TNF-alpha, IL-1beta, and IL-18, and promoted a Th1 response that was independent of IL-12p70 and IL-18, but substantially inhibited by IFN-alpha neutralization. Furthermore, immature IFN-DCs induced a potent autologous Ag-specific immune response, as evaluated by IFN-gamma secretion and expansion of CD8(+) T cells specific for CMV. Also, IFN-DCs expressed a large number of Toll-like receptors (TLRs), including acquisition of TLR7, which is classically found on the natural type I IFN-producing plasmacytoid DCs. Like plasmacytoid DCs, IFN-DCs could secrete IFN-alpha following viral stimulation or TLR7-specific stimulation. Taken together, these results illustrate the critical role of IFN-alpha at the early steps of immune response to pathogens or in autoimmune diseases.     

Vasoactive Intestinal Peptide Promotes Immune Escape of MKN45 Cells by Inhibiting Antigen-Presenting Molecules of Dendritic Cells In Vitro

To investigate vasoactive intestinal peptide (VIP) effect on dendritic cells (DCs) to gastric cancer (GC) cells in vitro involving immune escape mechanism of GC, we observed DC-SIGN (CD209), Ii chain (CD74), MHC-II and collaborative costimulatory molecules CD40, CD80, CD86 expressions in DCs, which co-incubated with GC cells and VIP. Human umbilical cord blood (HUCB) were obtained from healthy volunteers and human mononuclear cells were isolated from HUCB by density gradient centrifugation. Monocytes were purified from mononuclear cells using adherence separation and were treated with recombinant human granulocyte–macrophage colony-stimulating factor (rh GM-CSF), recombinant human interleukin-4 (rh IL-4) to induce immature monocyte-derived DCs (moDCs). Recombinant human tumor necrosis factor (rh TNF-α) was added on the 5th day to induce mature moDCs. Mature moDCs were collected on the 10th day, and co-incubated with MKN45, VIP and mannan, respectively. CD1a and CD83 expressions were detected by immunocytochemistry. VIP, VPAC1, CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs were detected by immunocytochemistry and RT-PCR. VPAC1 was detected in DCs, but VIP did not detected in DCs. When DCs were co-incubated with MKN45 cells, MKN45 cells could inhibit DCs’ expressions of CD209, CD74, MHC-II, CD40, CD80 and CD86 in the mRNA and protein levels (p < 0.05), and VIP could further inhibit CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs in the mRNA and protein levels (p < 0.05). The inhibition could not been reversed by mannan. CD209 was positively correlated with CD74, MHC-II, CD40, CD80 and CD86 in mRNA level and protein expression intensity in DCs. VIP could inhibit CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs, and inhibit antigen-presenting ability of DCs. VIP may promote immune escape of GC by inhibiting CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs.     

Changes in the proteomic profile during differentiation and maturation of human monocyte-derived dendritic cells stimulated with granulocyte macrophage colony stimulating factor/interleukin-4 and lipopolysaccharide

Dendritic cells (DCs) are highly specialized antigen-presenting cells that play an essential role in the immune response. We used the proteomic approach based on two-dimensional gel electrophoresis and mass spectrometry to identify the protein changes that occur during differentiation of DCs from monocytes (Mo) stimulated with granulocyte macrophage colony stimulating factor/interleukin-4 (GM-CSF/IL-4) and during the maturation of immature DCs stimulated with lipopolysaccharide. Sixty-three differentially expressed proteins (+/- two-fold) were unambiguously identified with sequence coverage greater than 20%. They corresponded to only 36 different proteins, because 11 were present as 38 electrophoretic forms. Some proteins such as tropomyosin 4 and heat shock protein 71 presented differentially expressed electrophoretic forms, suggesting that many of the changes in protein expression that accompany differentiation and maturation of DCs occur in post-translationally modified proteins. The largest differences in expression were observed for actin (21-fold in Mo), Rho GDP-dissociation inhibitor 2 (20-fold in Mo), vimentin (eight-fold in immature DCs), lymphocyte-specific protein 1 (12-fold in mature DCs) and thioredoxin (14-fold in mature DCs). Several proteins are directly related to functional and morphological characteristics of DCs, such as cytoskeletal proteins (cytoskeleton rearrangement) and chaperones (antigen processing and presentation), but other proteins have not been assigned specific functions in DCs. Only a few proteins identified here were the same as those reported in proteomic studies of DCs, which used different stimuli to produce the cells (GM-CSF/IL-4 and tumor necrosis factor-alpha). These data suggest that the DC protein profile depends on the stimuli used for differentiation and especially for maturation.     

Defective dendritic cell function in HIV-infected patients receiving effective highly active antiretroviral therapy: neutralization of IL-10 production and depletion of CD4+CD25+ T cells restore high levels of HIV-specific CD4+ T cell responses induced by dendritic cells generated in the presence of IFN-alpha

We previously demonstrated that GM-CSF/IFN-alpha combination allowed the differentiation of monocytes from HIV-infected patients into dendritic cells (DCs) exhibiting high CD8(+) T cell stimulating abilities. The present study was aimed at characterizing the ability of DCs generated in the presence of GM-CSF and IFN-alpha to induce CD4 T cell responses. DCs were generated from monocytes of HIV-infected patients in the presence of GM-CSF with either IFN-alpha (IFN-DCs) or IL-4 (IL-4-DCs) for 7 days. Eleven patients receiving highly active antiretroviral therapy and exhibiting CD4 cell counts above 400/mm(3) and plasma HIV-RNA <50 copies/ml for at least 1 year were included in the study. Both DC populations were found to be defective in inducing autologous (in response to tuberculin or HIV-p24) or allogeneic CD4 T cell proliferation. Neutralization of IL-10 during the differentiation of IFN-DCs, but not during the DC-T cell coculture, significantly increased their ability to stimulate autologous CD4 T cell proliferation in response to tuberculin and allogeneic CD4 T cell proliferation (4.1-fold and 3.0-fold increases, respectively, at the DC to T cell ratio of 1:10). Moreover, IL-10 neutralization and CD4(+)CD25(+) T cell depletion synergistically act to dramatically increase HIV-p24-specific CD4 T cell responses induced by IFN-DCs (31.7-fold increase) but not responses induced by IL-4-DCs. Taken together, our results indicate that IFN-DCs are more efficient than IL-4-DCs to stimulate CD4(+) T cell proliferation, further supporting their use for immune-based therapy in HIV infection.     

Dendritic cell-specific ICAM-3-grabbing nonintegrin expression on M2-polarized and tumor-associated macrophages is macrophage-CSF dependent and enhanced by tumor-derived IL-6 and IL-10

Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN; CD209) is a human pathogen-attachment C-type lectin with no obvious murine ortholog and for which ligation leads to enhanced anti-inflammatory cytokine release and altered proinflammatory cytokine production. Although induced by IL-4 in monocytes and considered as a DC marker, DC-SIGN expression on human APCs under homeostatic conditions is so far unexplained. We report in this study that M-CSF enhances DC-SIGN expression on in vitro derived anti-inflammatory macrophages and that M-CSF mediates the induction of DC-SIGN by fibroblast- and tumor cell-conditioned media. The M-CSF-inducible DC-SIGN expression along monocyte-to-macrophage differentiation is dependent on JNK and STAT3 activation, potentiated by STAT3-activating cytokines (IL-6, IL-10), and abrogated by the M1-polarizing cytokine GM-CSF. In pathological settings, DC-SIGN expression is detected in tumor tissues and on ex vivo-isolated CD14(+) CD163(+) IL-10-producing tumor-associated macrophages. Importantly, DC-SIGN Abs reduced the release of IL-10 from macrophages exposed to Lewis(x)-expressing SKBR3 tumor cells. These results indicate that DC-SIGN is expressed on both wound-healing (IL-4-dependent) and regulatory (M-CSF-dependent) alternative (M2) macrophages and that DC-SIGN expression on tumor-associated macrophages might help tumor progression by contributing to the maintenance of an immunosuppressive environment.